Hi Rishi,
The people who automatically get emails are the Project Managers and the person to whom the call is logged.
The user can click on the notifications tab on the issue screen and can choose to receive notifications.
In version 0.7.921.0 project managers can assign additional people to receive notifications.
About your group question. One way of doing this is to create groups on your email server.
Call them Project1Group@domain.com and Project2Group@domain.com then assign the correct members to the groups.
Then create two users in BugNet (Group1 and Group2) and assign the group you want to the notification on the issue.
Let me know if this helps.
Stewart Moss